SYRPHIDAE OF OKLAHOMA (DIPTERA)

Daniel A. Shorter and W. A. Drew

Keys to the subfamilies, tribes, genera, and species of Oklahoma Syrphidae are presented. Some species not known to Oklahoma but likely to occur here are included. County distribtuion and seasonal data are also given for the species included.

The flies of the family Syrphidae constitute one of the largest families of Diptera and are commonly collected in Oklahoma. Because of the large size of the family and the lack of current keys pertaining to the family as a whole for North America, this preliminary study is to provide keys for those persons interested in identifying Syrphidae collected in Oklahoma and to provide data regarding the distribution of Oklahoma Syrphidae.

Synonymy is not presented since it is available in the current catalog on North American Diptera [Stone et al. (1)]. In genera that have just one species in the Oklahoma fauna the characteristics of the species are not presented, as also is the case with species that are very easily identified by the keys with no further descriptions needed.

Characteristics: Small (3 to 8 mm), medium (8 to 15 mm), or large (more than 15 mm) flies, most of which have a false or spurious vein (vena spuria of European authors), extending longitudinally and slightly diagonally between the third (R4+5) and fourth (M1+2) longitudinal veins; spurious vein absent or nearly so in some Chrysogaster, Syritta, and Psilota, and in all Graptomyza (Asiatic and African genus), faint in others (e. g., some Volucella); bristles (macrochaetae) rarely present on any part of the body, never on head.

Head variable, usually as broad as or a little broader than thorax, often with epistoma produced downward, and sometimes forward; three ocelli always present; eyes large, bare or pilose, usually holoptic in males, always dichoptic in females; in some genera (e. g., Microdon, Mallota, and Helophilus in Oklahoma) males dichoptic, but front (space between eyes lying above antennae and limited by vertex or top of head; frons of some authors) different, always being narrower and forming some angularity with eyes, in females front broader and lateral margins straight; front never excavated, often swollen, sometimes with a short or long process which bears the antennae; antennae short or elongate, approximate at their bases, composed of three segments (or joints), usually with a bare, pubescent, or plumose dorsal arista, rarely with a terminal style; face (front of head between mouth and antennae and limited on sides by compound eyes and cheeks) (facies of some authors) broad, bare, pollinose, or pilose, sometimes excavated in profile beneath antennae and projecting below, or with a distinct tubercle or carina; frontal lunule absent or rudimentary; oral opening large, proboscis usually short (long in Rhingia); thorax rather large and robust, moderately arched, rarely with bristles; scutellum large, usually convex, often translucent, rarely with spines on border; wings comparatively large, marginal (R1) cell open or closed, third (R4+5) vein straight or dipped into apical (R5) cell, never branched, fourth (M4+5) vein terminated in third at or near its tip, three posterior cells present (R5 or apical, 1M2 or discal, and Cu1), basal (R, 2M, and 1A) cells long, anal (1A) cell always long and closed before margin of wing, between third and fourth longitudinal veins and nearly parallel to them, a strong fold or spurious vein nearly always present and characteristic of the family, not found in members of any other family; squamae (also called alulae, calpyters, or post-alar membranes) small to moderately large, with forked and fan-like ciliation; plumulae (a pair of elongated, fringed, filamentous projections from upper margin of pteropleura

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beneath squamae) peculiar to Syrphidae, although sometimes lacking; legs weak to moderately strong, occasionally very strong, never elongate; abdomen variable in shape, composed of five or six visible segments, rarely only four, generally thinly pilose or bare, sometimes with thick pile; hypopygium rarely prominent, although often large.

Key to Subfamilies of SYRPHIDAE

Head fitting close to thorax, and humeral calli of the latter bare of hairs; abdomen in both sexes with at least five visible not-transformed segments, in a few cases more than five; spiracle of third abdominal segment located in middle of pleuron

Syrphinae

Head not fitting closely to thorax, and humeral calli of the latter pilose; abdomen of males with not more than four visible not-transformed segments, of females not more than five; spiracle of third abdominal segment located at or near anterior margin of pleuron

Milesiinae

Subfamily SYRPHINAEKey to Tribes of Oklahoma (modified from Williston (2))

Male genitalia long, projecting, asymmetrical as seen from above, somewhat cylindrical; abdomen of female broadly oval, fifth segment half as long as fourth

Eupeodes

Male genitalia normal; fifth abdominal segment of female usually less than half as long as fourth; if about half as long, abdomen with subparallel sides and front not whitish-yellow immediately above antennae

Characteristics: This might be called the "typical" genus of the family. Medium-sized species (8-15 mm); moderately hairy; almost always bright yellow marked; head as broad, or broader than, thorax, slightly excavated behind; face gently bulging below, with a low tubercle, usually yellow,

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rarely with medium dark vitta, frequently micropubescent; antennae short, inserted above middle of face; arista inserted near base of oval third joint, third joint and arista microscopically hairy; eyes usually bare, sometimes slightly hairy, holoptic in male; thorax quadrate or nearly so, humeri and area between without pile, side margins of thorax often yellowish, mesonotum often with pollinose median vittae; yellow or brownish-yellow scutellum largely convex and semicircular, with fringe of hairs below margin, no bristles on thorax or scutellum, metasternum bare; wings simple, third vein only slightly curved, anterior cross-vein located well before middle of discal cell, spurious vein distinct, marginal cell broadly open; squamae large, lower lobe with dense short hairs and a few long hairs above (this character should not be confused with long hairs on margin of squamae): legs simple, slender, hairy, tarsal claws and pulvilli well developed; abdomen black, oval, emarginate on at least second and third segments, rather flattened, with prominent yellow crossbands or spots, usually with one pair of large yellow spots on second abdominal tergite, with stripes or spots on following tergites.

Key to Species

1.

First segment of middle basitarsi with only yellow spicules beneath; sides of mesonotum distinctly yellow pollinose

Characteristics: Length, 8-10 mm; very similar to Syrphus ribesii (Linnaeus) except for median dark vitta on face and median brown area on hind femora of female; males never with black pile on face except on sides near antennae; dark spots below eyes wanting; hind femora of males black on more than basal three-fourths.

County records: Ottawa (June).

Metasyrphus Matsumura

Characteristics: This is a very large genus in North America and rather difficult to work with as there are many intermediate forms between species. Very similar to Syrphus Fabricius in size, coloration, and general appearance; face yellow, gently bulging below, with a low tubercle, with or without black, shining, median vitta; vertex usually black, pile of front and vertex usually dark; antennae oval, inserted well above middle of face, third joint and arista micropubescent; eyes usually bare, sometimes lightly pilose, holoptic in male; thorax usually shining, without conspicuous longitudinal vittae, metasternum usually pilose; lower lobe of squamae sometimes covered with dense pubescence above, but without long hairs on disc; third vein straight or only slightly curved into apical cell, anterior cross-vein before middle of discal cell; legs simple; abdomen emarginate, oval, with prominent yellow spots or crossbands, rarely reddish, usually with a pair of yellow spots on second abdominal tergite.

Characteristics: Length, 10-11 mm; face with median black vitta, front with two large black spots just above base of each antennae, at least in male; eyes bare; thorax steely-blue, shining, pile of thorax white, although a few black hairs sometimes seen on male just above wings; scutellum yellowish to opalescent, darker at basal corners, mostly black pilose in male, frequently wholly yellow-pilose in female; metasternum pilose; third vein only gently curved; abdomen with three pairs of spots, all separated from side margins.

Characteristics: Length, 9-11 mm; antennae slightly larger than in M. americanus; pile of face predominantly pale, black of cheeks of male usually connected to black vitta of face; abdominal bands are narrower than in M. americanus and posterior margins of second and third distinctly emarginate; genital styli small, oval.

County records: Payne, Woods (March-May).

Metasyrphus americanus (Weidemann)

Characteristics: Length, 9-12 mm; face with median black vitta, front in male heavily pollinose, with small dark dot just above base of each antenna, front in female with broad pollinose band distinctly interrupted to form inverted black Y, with two prominent black dots above antennae; antennae rather large, third joint one and one-half times as long as first two segments combined, black, yellowish on lower one-third of last segment; arista reddish, darker apically; scutellum yellowish; with rather fine, somewhat kinky, yellow and black intermixed pile, the yellow pile predominant; metasternum pilose; legs of male yellow, with one-fourth of front and middle femora, three-fourths to four-fifths of hind femora, and a broad median band on hind tibiae black; legs of female more yellowish, with only basal one-fifth of front and middle femora, a broad median ring on hind femora, and a narrow ring on hind tibiae black, abdominal bands broad, almost straight, and separated from side margins, first abdominal band frequently entire; genital cerci long and yellowish-red, styli long and fairly slender.

Characteristics: Very similar to some species of Metasyrphus. Length, 7-10 mm; head hemispherical; face slightly concave below antennae, tuberculate, whitish-yellow, with black cheeks and dark median vitta over tubercle; antennae short, third joint oval; dark crescent-shaped spot over base of each antenna; eyes bare, holoptic in male; thorax pilose; scutellum raised, exposing metanotum; marginal cell open, anterior cross-vein near base of discal cell, third vein gently curved; legs simple, reddish, base of femora black; abdomen black, first segment, lateral and posterior margins of all segments shining, the fifth wholly shining, two yellow oblong spots on second abdominal segment well separated from lateral margin, on each of two following segments a pair of longer, oblong yellow spots, those on segments three and four very slightly lunate, posterior margins of fourth and fifth segments narrowly yellow, sixth segment shining black, sparsely set with whitish pile, in male sixth segment as long as two preceding segments together, but narrower, almost tubular from above, asymmetrical, end pointing slightly to insect's right as seen from above, in female abdomen elliptical, fifth segment about half as long as fourth.

Characteristics: Medium-sized to moderately large Syrphus-like flies. Head broader

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than thorax; face yellow, with or without median dark vitta, not narrowed below; arista basal; eyes usually bare, sometimes pilose; metasternum usually bare, sometimes pilose; lower lobe of squamae without long hairs on upper surface, but usually short hairs present; abdomen oval, usually slender, emargination indistinct or lacking, sometimes with sides of abdominal tergites rolled under.

Characteristics: Small, somewhat elongate species, thinly pilose, shining black, with yellow markings on head, thorax, and abdomen; head hemispherical, small, narrow, yellow, rarely darker centrally, produced bluntly or acutely; antennae located near middle of head in profile, short, third joint oval; arista basal, bare; eyes bare, narrowly contiguous in male midway between antennae and ocelli; ocelli in both sexes remote from vertex; dorsum of thorax with a median cinereous linear stripe and lateral yellow margins; humeri yellow, usually with yellow extending posteriorly to transverse suture or beyond; wings as in Syrphus, third vein usually gently sinuous; legs simple, rather slender, hind femora in male sometimes thickened and arcuate; abdomen oval to subcircular, but more often slender or even subpetiolate or spatulate, very variable in coloring, usually yellow or orange, marked with black or brown spots or fasciae or vittae or a combination.

Characteristics: This genus appears to be much like the genus Mesograpta, from which it can be separated by the enlarged hind legs of the male and the black band on the hind femora of the female as given in the key to the genera and by the shape of the apical region of the abdomen of the female. Small, mostly shining black, elongate species; face small, produced medially; antennae small, third joint oval; scutellum black with a yellow border; hind femora arcuate and thickened, hind tibiae of male greatly arcuate and dilated at tip, hind femora of female with a black band.

Characteristics: Small to large (3-20 mm), dark, light, or metallic-colored species; head large and round, broader than thorax; face and front narrow, face narrowed below, usually tuberculate; antennae short, third joint rounded or oval; arista toward base, slender, bare; eyes bare, holoptic in male, narrowly dichoptic in female; thorax short, metasternum bare; wings often with dark brown or blackish markings; legs simple, very slender, hind femora elongate, but not thickened, hind metatarsi elongated and thickened; abdomen slender, usually three or four times as long as thorax, usually petiolate, sometimes spatulate, second segment very slender, third gradually widening to tip of fourth segment, remaining segments less robust. Genus contains many species groups.

Characteristics: Length, 9-11 mm; most common and widely distributed species of Baccha in North America; frontal triangle considerably longer than contiguity of eyes, front in female very narrow at vertex; face nearly perpendicular, very gently concave below antennae to tubercle; antennae inserted near middle of head in profile; eyes convergent below; wings almost wholly dark except posterior corner of apex in most males, and dark on at least anterior half and extending broadly to posterior margin at middle in female; considerable variation in exact amount and intensity of infuscation on wings and body, but on the whole a dark species; abdomen slender, only a little widened behind, fifth segment scarcely longer than broad in both sexes.

Characteristics: Small, rather short, dark species; perhaps the smallest syrphid fly; rarely any light coloration; head broader than thorax, hemispherical, somewhat flattened; face short, weakly produced below, slightly tuberculate, may be pale yellow; antennae short, with third segment as long or longer than first two together; arista before middle, bare; eyes pilose, narrowly contiguous in male; marginal cell open, third vein straight, anterior cross-vein near base of discal cell, apical cross-vein sinuate, terminating in third vein in nearly a right angle, at a considerable distance before the tip; legs rather short, mainly short haired, anterior femora with longer hairs on postero-ventral side, hind femora with longer hairs on antero-ventral side, hind metatarsi a little thickened; abdomen bent down apically, more or less reddish, hypopygium small.

Characteristics: Small to medium, weak-flying species of dark coloration, occasionally with paired yellow spots on abdomen; front and vertex sometimes swollen; face flattened, not tuberculate, broader at oral margin than at antennae, or more narrow and about as wide below as at base of antennae; antennae short, not longer than head, with third segment elongate; arista microscopically pilose or bare; eyes evenly pilose or with horizontal bare stripe; wings rather short and broad, marginal cell open, third vein nearly straight, or gently curved, anterior cross-vein before middle of discal cell; middle of hind coxae and trochanters with or without processess, hind femora slender or somewhat enlarged, minutely spinose or toothed and compressed apically below.

Key to Species

Face considerably broader at oral margin than at antennae

femoralis

Face but little or not at all broader at oral margin than at antennae

banksi

Pipiza femoralis Loew

Characteristics: Length, 8-9 mm; moderately pilose species; pile sparser and shorter in female; face whitish pilose; antennae rather large, two basal joints reddish, third joint black, obscurely red near base; arista black, pallid near base; wings faintly or moderately brownish clouded across middle, fading out apically and posteriorly, almost hyaline in some specimens, more distinctly clouded in female; hind femora considerably thickened, bearing spinules near apex, usually on a plate-like process; male usually, female always, with two yellow spots forming an arcuate band on second abdominal tergite, spots separated by a black line, and separated from the lateral margins by a black border.

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County records: Payne (April).

Pipiza banksi (Curran)

Characteristics: Length, 4-5.5 mm; frontal triangle broadly opaque above, the lower margin angulated; third antennal joint about three to four times as long as wide, basal antennal joints yellowish; bare stripe of eyes broad; wings hyaline; yellow segments of tarsi wholly without black hairs or bristles, pile on hind basitarsi very long and prominent.

Characteristics: Medium-sized to moderately large, bright brassy or golden species, with strong bristles on pleura, post calli and scutellum; head broader than thorax; face much like that of Syrphus, slightly concave, with long, low, gradually rounded

Characteristics: Small flies, always dark in color, usually metallic; wholly without yellow markings except on legs; head hemispherical, broader than thorax; distinctly characterized from all other genera by front in female having transverse lateral wrinkles; epistoma projecting greatly in females, less so in males; antennae not longer than head, third antennal segment often quite elongate; eyes bare, often with zig-zag or linear pattern, holoptic in male; scutellum gently thinned above near its border, sharp, sometimes wrinkled on its disk; third vein straight, spurious vein often faint, anterior cross-vein before middle of discal cell; abdomen short, oval, flattened, border rounded, not thinned.

Key to Species

Apical cross-vein joins third vein beyond tip of second vein; eyes with a median, straight, horizontal line and two vertical, labyrinthine, brown lines; antennae longer than face, second joint nearly as long as third

nitida

Apical cross-vein joins third vein opposite or before tip of second vein; eyes with very faint markings, or none; antennae elongate, considerably longer than face, third joint almost three times as long as second

Characteristics: Medium-sized flies, nearly bare, of reddish-yellow, sometimes brownish color; head narrower than thorax; face moderately produced downward and forward, concave nontuberculate, front in female narrowed above; antennae short, third segment oval, rarely more roundish; arista basal, bare, pubescent or short plumose; eyes bare, holoptic in male; thorax a little narrowed in front, usually with some stouter hairs on mesopleura above, on postalar calli and margin of scutellum, which is rather large, squarish or more or less triangular; wings longer than abdomen, anterior cross-vein before middle of discal cell, apical cell ending in an acute angle near apex of wing; squamae of medium size; legs simple, femora a little thickened, and usually with short bristles below, especially hind pair; abdomen roughly triangular in shape, broader and not much longer than thorax, broadest at second segment, then quickly narrowing to apex, but less so in female.

Characteristics: Very large genus containing bare to very pilose species varying from very small to large (6-16 mm); head broader than thorax, produced downward and rarely forward, conical, pointed at tip; front sometimes swollen and inflated; face usually concave above, with either a large rounded tubercle below, or a rounded protuberant bulge, merging into epistoma; antennae small, third segment elongate, sometimes narrowed medially, arista always plumose; eyes pilose, sometimes bare in female, holoptic in male; dorsum of thorax with a pair of yellow stripes in most species, scutellum large, usually translucent, both thorax and scutellum with numerous bristles; marginal cell closed, anterior cross-vein usually towards base of discal cell and rectangular, third vein straight; legs simple; abdomen short, wide, oval, convex, inflated, slightly longer than thorax, often nearly circular.

Pleura of male mostly or wholly yellow-pilose; abdomen of both male and female ferruginous or brown with green and violet opalescence, base pale; basal two visible sternites yellow, or if dark then first sternite brown, second yellow in middle; lower lobe of squamae yellow to orange; scutellum pale pilose

vesicularia

Volucella fasciata Macquart

Characteristics: Antennae yellow, brownish toward tip; legs black, knees, basal portion of tibiae, and first three segments of all tarsi, yellow; abdomen with three rather broad yellow bands, anterior one on second tergite broadest, widest toward middle, interrupted or subinterrupted, others on anterior part of third and fourth tergites, entire; venter, in addition to broad basal band, with one on third segment.

Antennae remarkably elongate, with first two segments almost equal in length, third segment short, less than half length of first segment; mesonotum black, with two interrupted vittae forming four elongate, yellowish spots; scutellum broadly yellow apically; abdomen with alternating black and yellow fasciae

Sphecomyia

Antennae not remarkably elongate, or if elongate then thorax without median pair of interrupted yellow vittae

Face never with well-developed median keel and lesser face cheek keels; without above combination of characters

3

3.

Hind femora black, greatly swollen, with numerous spines below, with base and a usually incomplete ring near middle reddish-yellow; face weakly carinate or with obtuse, longitudinal ridge, never with a keel, epistoma slightly produced; rather small (7-8 mm), slender, black, nearly bare species with yellow markings

Syritta

Face not carinate or ridged; hind femora slender or swollen, never colored as above

Hind femora slender, with a subapical tooth; eyes with vertical, irregular stripes or blotches; first and second antennal segments slightly to distinctly elongate; metasternum with an obtuse blunt spur anteriorly; bright, wasp-like flies

Spilomyia

Hind femora often thickened, with or without subapical tooth; eyes uniformly colored; antennae scarcely or not at all elongate; face usually concave, front produced; marginal cell closed, apical cell closed near costal border before apex of wing, third vein gently looped into apical cell; large (16-22 mm), brightly colored flies

Milesia

7.

Bright, wasp-like flies, with yellow-pollinose markings on thorax and abdomen; first and second antennal segments always quite short; face usually quite concave, especially in females, less so in males; males often with weak tubercle, face never deeply produced; anterior wing border dark

Temnostoma

Never yellow-pollinose, although sometimes marked with yellow

8

8.

Abdomen with large, transverse or oblique, yellow spots on at least second, third and fourth tergites

Somula

Abdomen without large, transverse or oblique, yellow spots on second, third and fourth tergites

9

9.

Hind femora compressed below on distal third or more into narrow, spiniferous ridges, straight but much thickened; abdomen not constricted basally

Characteristics: Slender, medium to large species; head hemispherical; front in female narrowed above; face concave in profile, not tuberculate, oral margin projecting, but not as far forward as the antennae prominence; antennae situated on a prominent conical projection, first two joints short, third joint rather large, oval; eyes bare, holoptic in male; thorax large, as wide or wider than abdomen; marginal cell open, anterior cross-vein at or beyond middle of discal cell, third vein straight or gently curve; legs stout, hind femora elongate and thickened, with a row of spines below, hind tibiae arcuate, often ending in a spur; abdomen flattened, elongate, with sides parallel.

Characteristics: Length, 9-10 mm; distinguished from closely related species by arista, which is yellowish basally, dark distally; posterior calli without conspicuous black hairs; anterior and middle tibiae entirely or largely yellowish, hind femora of male with a double row of long anteroventral spines extending almost entire length and all about equally long and rather evenly spaced.

Characteristics: Relatively large species, with bright yellow spots or bands on abdomen and thorax, and with strong superficial resemblance to vespid wasps found in the same region, also with similar actions, even to habit of resting on the four posterior legs and waving front legs about in almost the same way that vespids move their antennae, head hemispherical, broader than thorax; face nearly straight in profile, minutely produced at epistoma or with a minute tubercle in middle; antennae porrect, with first and second segments elongate, third segment rounded, not twice as long as broad; arista bare, eyes bare and marked with irregular vertical stripes or bands of spots, holoptic in male; thorax short and broad, considerably convex above, with yellow spots; scutellum with or without fringe; metasternum pilose, with a blunt angular tubercle in front; marginal cell widely open, apical cell not petiolate, vein beyond tip of anal cell continued outward, nearly parallel to hind border of wing, anterior third to half of wing brown, brownish-yellow, or at least darkened; hind femora simple, with a prominent subapical, dentate spur; abdomen convex, large, subcylindrical and elongate, with yellow bands.

Key to Species

Anterior orange fascia on second abdominal segment carried very broadly forward laterally, almost to base of segment; black markings behind second segment linear; yellow spots on pleura not continuous from hypopleura to sternopleura

texana

Anterior yellowish fascia on second abdominal segment gradually widened laterally; black fascia as wide as yellow ones; all yellow cross-bands entire; yellow spots on pleura form a continuous line from hypopleura to sternopleura

longicornis

Spilomyia texana Johnson

County records: McCurtain, Pushmataha (April-June).

Spilomyia longicornis Loew

County records: Payne (June).

Temnostoma Lepeletier and Serville

Characteristics: Medium to large, wasp-like flies; characteristically marked with yellow or gray pollen; face concave in female, often with weak tubercle in male; antennae short, inserted in middle of head, third segment nearly or quite orbicular; eyes bare, narrowly dichoptic; scutellum black, with fringe; metasternum pilose, tending to become pubescent in a few species which have only a very few hairs; apical cell not petiolate, anterior cross-vein near middle of discal cell, no stigmatic cross-vein; hind femora simple, without any process below; abdomen elongate, becoming more slender in smaller species.

about 20 mm; head hemispherical, broader than thorax; face large or well developed in profile, usually nearly straight or concave above, face prominent upon lower half but never greatly produced downward; antennae short, porrect, inserted on projection of front, third segment orbicular or a little wider than long; eyes bare, usually holoptic in male; thorax large and robust, with yellow markings; scutellum largely yellow, with fringe; metasternum pilose; wings comparatively narrow, venation characteristic, apical cell petiolate or nonpetiolate, marginal cell closed, anterior cross-vein very oblique, joining discal cell in distal one-fourth; hind femora elongate and stout without being noticeably thickened, femora frequently with a small, subapical, dentate projection; abdomen elongate, more than twice as long as thorax, only a little broader in middle, with yellow bands.

Characteristics: Similar to M. virginiensis, but readily distinguished by almost wholly reddish-yellow scutellum, which, at most, has only a very narrow black line basally; by different maculation of thorax; and by black transverse markings of abdomen, especially those of second tergite, which are considerably narrower than in M. virginiensis; wings usually more heavily tinged with blackish brown along leading edge; width of abdomen variable; front of female with black median vitta.

County records: Latimer, Pushmataha (May-June).

Milesia virginiensis (Drury)

Characteristics: Bright yellow and black wasp mimics; thorax and abdomen distinctive; as in M. scutellata, width of abdomen variable in both sexes.

Front of male much wider than width of antennal process; female with yellow pile on lower portion of front

latifrons

Front of male as narrow or narrower than width of antennal process; front of female entirely black pilose

fasciatus

Helophilus latifrons Loew

Characteristics: Length, 11-15 mm; front of male only black pilose across ocelli, front of female yellow pilose on lower third; face with median line always yellow or reddish-yellow, never ferruginous or black; second and third abdominal segments chiefly lemon yellow in male, variable in female.

Characteristics: Length, 10-15 mm; similar to H. latifrons, but abdominal bands usually narrower; front much narrower and black pile covering all of front above depression in male and all of front in female; legs more extensively black than in H. latifrons.

Characteristics: Rather small, slender, dark species; ocellar triangle in female rather small, rarely almost equilateral; front of female about width of one eye, front of male not half width of one eye; eyes bare, always dichoptic in both sexes; thorax with light pollinose stripes on dorsum; stigmal spot simulating a cross-vein, marginal cell open, third vein deeply bent into apical cell, anterior cross-vein oblique, located beyond middle of discal cell; apex of hind tibiae produced into scoop-like or rather acute spur; abdomen elongate, more than twice as long as wide, sides parallel, slightly tapering at apex.

Abdomen entirely black-pilose except for a few hairs on anterior angles of second tergite

bautias

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Abdomen slightly to considerably yellow-pilose beyond second tergite

facialis

Mallota posticata (Fabricius)

Characteristics: Length, 11-15 mm; eyes holoptic in male for a little longer distance than in M. bautias; abdomen black, with abundant black and yellow pile, yellow pile quite variable, usually confined to first and basal part of second tergite, at other times covering nearly entire third tergite, when denuded of pile abdomen often with considerable red on second and third tergites.

County records: McCurtain, Pawnee (May-June).

Mallota bautias (Walker)

Characteristics: Length, 12-16 mm; fairly common species; males dimorphic, in one form (usually smaller specimens) hind tibiae moderately compressed and wholly without a spur in middle; in other form, hind tibiae extraordinarily compressed and with a stout angular projection in middle which when tibia is flexed, lies on outer side of femur; flight distinctive, occurring with a loud buzz, going in and out about patches of flowers and through low-growing vegetation.

County records: Logan, McCurtain, Pawnee, Payne, Woods (April-June).

Mallota facialis Hunter

Characteristics: Some authors express doubt that this is a valid species distinct from M. bautias. It shows considerable variation in amount of yellow pile on abdomen; some specimens have only scattered yellow hairs while others have almost entire abdomen covered with yellow pile. Typical specimens have the last segment of males and the last two segments of females pale orange to yellow pilose.

Characteristics: This is a large and cosmopolitan genus including more than four hundred described species; generally medium, occasionally large flies; length, 7-17 mm; moderately hairy or sometimes densely velvet pilose; head broader than high and about as broad or slightly broader than thorax; face tuberculate, concave upon upper half to a varying extent, and slightly produced downward and diagonally forward, the amount also varying; antennae short, inserted near middle of head, third segment longest ventrally, while dorso-apically it is shorter and rounded; arista long, bare or microscopically pubescent, rarely short plumose basally; eyes range from bare to pilose, with or without bare bands, from unicolorous to dark vertical bands or numerous spots on a lighter ground color, holoptic to narrowly dichoptic in male; mesonotum short and compact, rather convex; scutellum without fringe; stigmatic cross-vein present, spurious vein generally distinct, marginal cell closed, third vein deeply bent into apical cell and ending well above apex of wing, anterior cross-vein at or near middle of discal cell; hind femora slender to moderately thickened and without spurs, spines, or teeth, apically the ventral margin often setiferous; tibiae nearly straight or moderately arcuate; abdomen generally with yellow and black markings.

Key to Species

1.

Eyes spotted; abdomen wholly shining greenish or brassy

aeneus

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Eyes not spotted; abdomen not wholly shining greenish or brassy

2

2.

Arista distinctly plumose on basal half, with some filaments as long as or longer than first antennal segment

transversus

Arista bare, pubescent or short pilose (filament not longer than first antennal segment)

Wings sometimes slightly clouded medially, but not with a distinct, approximately quadrate dark spot; eyes with a distinct, broad, vertical band of dark yellowish pile more dense than rest of ocular pile; like honeybees in appearance

tenax

5.

With an ashy or metallic fascia situated between the scutellum and transverse suture

vinetorum

Without a prescutellar band

latifrons

Eristalis aeneus (Scopoli)

Characteristics: Length, 8-10 mm; separated from other Oklahoma Eristalis by the eyes, which are covered with numerous, small, dark spots that tend to run together on upper part of eyes.

County records: Beaver, Grady, Payne, Woods (March-November).

Eristalis tenax (Linnaeus)

Characteristics: Length, 12-15 mm; complete facial stripe; eyes with dark pile, more abundant near middle, in form of an elongated, vertical stripe or ellipse, the middle of which is less pilose.

Characteristics: Very common, characteristic species; length, 9-14 mm; antennae black; arista bare to microscopically pubescent; facial vittae and cheeks shining black; thorax greenish-brown, shining, with no traces of opaque markings; scutellum yellowish-brown; wings sometimes hyaline, usually with a brownish spot in middle of anterior half; abdomen wholly shining except for an interrupted opaque posterior band on second segment, occasionally an oval, opaque spot on each side of third segment in male.

We also thank the Snow Entomological Museum, University of Kansas; the Stovall Museum, The University of Oklahoma; the Entomological Museum, Kansas State University; and the Chicago Natural History Museum for the loan of specimens and use of their facilities, and Dr. Yale S. Sedman of Western Illinois University for his assistance and suggestions.